Trouble running a bash script with crontab

Question

I have a bash script that checks to see if my PHP service is running, and starts it if needed.

#!/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

KP=$(pgrep -P 1 -f script.php)
if [ "X$KP" = "X" ]
    then
        /usr/bin/nohup php /var/www/test/script.php >>/var/www/test/log.txt 2>&1 &
fi

I then added the following entry to crontab -e (as my user).

* * * * * /var/www/test/startup >> /var/www/test/cron.log 2>&1 &

The cron runs, and I can see the process when looking at htop. However, it doesn't seem to be working or writing to the logs. It just sits there using 0% of the CPU. the /var/www/test/ folder is owned by my and the log files have 666 permissions.

What is wrong? Or rather, what can I change to get the error logs working so I know what's wrong?

if you run the code manually from command line, it works? ` /usr/bin/nohup php /var/www/test/script.php >>/var/www/test/log.txt 2>&1 & ` — Crazy_Bash
– Crazy_Bash, Commented Oct 2, 2012 at 21:03
@Crazy_Bash, the output was [1] 1858 (the pid) and the process is running. It also seems to have written to the log.txt file. — Xeoncross
– Xeoncross, Commented Oct 2, 2012 at 21:08
But if it runs as normal user from CLI, why would it need to run as root from cron? — Barmar
– Barmar, Commented Oct 2, 2012 at 21:37

aqn · Accepted Answer · 2012-10-02 22:39:42Z

I suggest adding debugging stuff. Some possible failures are:

Can your user actually run the /var/www/test/startup script? Can your user write to /var/www/test/cron.log? I suggest just have the crontab entry as so:

* * * * * /var/www/test/startup

Any output (stdin and stderr) should be emailed to your user (unless sendmail is broken on this machine).

Where is pgrep? Is it in the path set by PATH=.... Ditto php

What is $KP? echo it to a log file that you know is writable:

touch /tmp/mylog
chmod 666 /tmp/mylog

then in the script:

echo "I'm getting pgrep from <`type -p pgrep`>" >>/tmp/mylog
echo "KP is now <$KP>" >>/tmp/mylog

Perhaps the script.php process is already running and is owned by PID 1?

Perhaps the script does not have write permission to /var/www/test/log.txt ? It does not matter that /var/www/test is owned by you or if /var/www/test/log.txt is 666, if one of the parent directory is not writable or executable by you. Double-check:

if [ ! -w /var/www/test/log.txt ]; then echo "Cannot write to /var/www/test/log.txt"; fi

Barmar · Accepted Answer · 2012-10-02 21:45:29Z

0

I suspect it has something to do with nohup. It only does its special things if standard input is a terminal. But I'm not sure why this would make a difference, since there's no need to detach the background process in a cron job.

But maybe this will help:

(/usr/bin/nohup php /var/www/test/script.php >>/var/www/test/log.txt 2>&1 &)

answered Oct 2, 2012 at 21:45

Barmar

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